Before Battlefleet Gothic, Games Workshop released Space Fleet in 1991.  It came with 4 plastic ships to build, 2 Imperial and 2 Eldar.  The lid of the box also was used for rolling the dice and was divided into 9 squares and where the dice stopped would determine if the attack hit or not.
GW followed up with articles in multiple White Dwarf magazine issues covering the background of the game a great deal of additional rules and stats and information on the line of metal miniatures that were produced by Citadel.  The articles were in issues 139, 140, 141, 146, 147 of White Dwarf.
The miniatures were quite interesting and the Imperial Fleet grew quite large with many new minis but also some of the support ships were actually re-used miniatures from QT Models whose ships had been aquired by Citadel like several of the miniatures in Citadel's Space Cruisers and C43 and C44 lines.
The Eldar fleet only got 2 ships, the metal version of the Wraithship, plastic ship in the box and a smaller Shadowhunter.
The Tyranid Hive Fleet defined in White Dwarf 146 was quite extensive and did feature several ships that had been part of Citadel's Space Cruiser line in the past.

'Spaceship Battles' Ships White Dwarf #225 included a preview for a starship game in the works from GW - the Spaceship Battles article.  That game would become Battlefleet Gothic but included in the article, were 3 ships used in the example images. Those 3 ships were clearly based on the Emperor Capital Ship miniature from Space Fleet.  The ship stats in the preview were closer to Battlefleet Gothic but the ship images have such a Space Fleet vibe, I'm including those here.  3D models you can print are available for these ships too. Agippa Battleship Basically a Emperor with 3 big turrets on each side with smaller than full broadside arcs so I represent them with K-Guns to spice things up. Iron Duke Battleship Looks like an Emperor miniature with wings added but the preview rules included prow torpedoes which are basically missiles so I'm giving them Salvo Missiles to make them different. Unclean Battleship Chaos ships appeared in the preview so this ship is the first Chaos fleet ship on the table.
AGRIPPA class Battleship Mass 146 Cost 547/614 Average Hull 40 (10/10/10) Armour 6 points Thrust 2 FTL 4 Fire Controls 1 ADFC 6 PDSs Level 2 Screens 2 Class 1 Beam Batteries 4 Class 2 Beam Batteries (2xPBS, 2xSBS,) 6 Class 2 Beam K-Guns (3xFP/AP, 3xFS/AS) 1 Class 2 Graser (F)
IRON DUKE class Battleship Mass 144 Cost 506/569 Average Hull 40 (10/10/10) Armour 6 points Thrust 2 FTL 4 Fire Controls 5 PDSs Level 2 Screens 2 Class 1 Beam Batteries 4 Class 2 Beam Batteries (2xPBS, 2xSBS,) 4 Class 3 Beam Batteries (2xPBS, 2xSBS) 1 Salvo Missile Launchers (FP/F/FS) 10 Mass Reloads
UNCLEAN class Chaos Battleship Mass 140 Cost 500/556 Average Hull 40 (10/10/10/10) Thrust 3 FTL 4 Fire Controls 1 ADFC 6 PDSs Level 2 Screens 2 Class 1 Beam Batteries 2 Class 2 Beam Batteries (PBS, SBS) 4 Class 3 Beam Batteries (2xPBS, 2xSBS) 1 Class 2 Graser (F)